Nowadays, vehicles/machines equipped with an internal combustion engine (e.g., a diesel engine) such as construction machines (e.g., hydraulic excavator and wheel loader), haulage vehicles (e.g., bus, freight truck, dump truck and on-road truck), and fixed power generators are provided with an exhaust gas purifying device in which particulate matter (PM) in exhaust gas from the internal combustion engine is removed through a diesel particulate filter (DPF). The exhaust gas purifying device is equipped with a pressure sensor (differential-pressure sensor) that detects a differential pressure in a filter used as the DPF between an inlet-side pressure and an outlet-side pressure of exhaust gas. Based on the differential pressure detected by the pressure sensor, the amount of PM deposited on the filter is estimated. For instance, Patent Literatures 1 and 2 disclose arrangements configured to determine a malfunction of a pressure sensor or a pressure-introducing hose connected to the pressure sensor.
Specifically, according to Patent Literature 1, it is determined whether or not there is a problem (i.e., hose damage) with a pressure-introducing hose connected to a pressure sensor for a DPF based on: a determination result on a malfunction of the DPF based on an inlet-side temperature and outlet-side temperature of exhaust gas in the filter; and a differential pressure detected by the pressure sensor.
According to Patent Literature 2, a duct connected to an outlet side of a filter is provided with a switch valve so that the filter can be exposed to atmospheric air and it is determined whether or not there is a malfunction of a pressure sensor based on a change in pressure at an upstream side of the filter when the filter is exposed to atmospheric air.
Thus, according to Patent Literatures 1 and 2, when it is determined that pressure is improperly introduced into the pressure sensor or the pressure sensor itself has a malfunction, a report on the malfunction is made to notify an operator of the malfunction. The operator may then call a serviceperson and ask him/her to do maintenance such as replacement of the pressure sensor or the hose.